Adolescents, and especially minority youth, are the fastest growing population for new HIV infection National Institutes of Health, 1997). Many HIV+ adolescents engage in high risk sexual behaviors and other transmission risk behaviors including substance use and medication non-adherence. Finding comprehensive interventions that effectively address sexual and other transmission risk behaviors in HIV+ adolescents is an important public health goal (Coates, 1998). Research indicates that transmission risk behaviors are multi- determined, with drivers occurring at individual, caregiver, peer, school, and community ecological levels. Thus, effective interventions will need to comprehensively target relevant drivers across these systems. The first aim of the present study is to adapt an empirically validated intervention, Multisystemic Therapy (MST;Henggeler et al., 1998) to address sexual risk behaviors by HIV+ adolescents. MST is an ecologically-based intervention originally designed to address serious juvenile delinquency by targeting drivers across all levels of youths'ecologies. The proposed adaptation will incorporate prior successful adaptations of MST for use with substance abusing/dependent youth and medication non-adherent youth. The second aim of this study s to conduct a pilot study with 50 HIV+ youths ages 11-17 years who receive treatment at one of two AIDS clinics in South Carolina and who engage in one or more transmission risk behaviors. Over 90% of the youth will be African American. Youth will be randomly assigned to the experimental (MST-HIV) treatment condition or to a comparison intervention that supplements treatment as usual (TAU) with a single session of Motivational Interviewing (Ml). Principal outcome measures will be collected through 9-months post- recruitment and will assess risky sexual behaviors, alcohol and drug use, and adherence to HIV medication regimens. If results support the efficacy of MST-HIV, a larger trial will be proposed to further examine cost and clinical effectiveness. HIV represents a serious public health concern, especially for minority youth. To reduce the spread of HIV, interventions must comprehensively target the multivariate drivers of transmission risk behaviors. MST is clinically and cost effective with serious problem behaviors, effectively overcomes services access barriers, is culturally competent, and available in most States. Thus, MST has the potential to provide an excellent platform on which to build and deliver effective adaptations for HIV+ youths.